System for the electric transmission of signals along lines for power distribution



July 10, 1928. 1,676,680

. J. BETHENOD SYSTEM FOR THE ELECTRIC TRANSMISSION OF SIGNALS ALONGLINES FOR POWER DISTRIBUTION Filed Jan. 4, 1923 I ejose o Be b61100? oerstares one JOSE PE nnrnnnon,

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, Application filed January 4,4923, SerialHo. 610,735, and in FranceFebruary 2, 1922.

. 'Thisinvention relates to'systems for the electric transmissionofsignals' applicable to distribution services with. a neutral wire andprimarily consists in, provision of a react- 5 ance coil between theneutral wire and the grounding of each transformer station, with a Viewto feeding receiving relays 'placed. with the subscribers by means'of acurrent source of relatively hi h frequency con- 1 nected to theterminals 0% the reactance coil,

the impedance of the latter being negligible at the periodicity of.thedistribution.

In the accompanying drawings, Figure 1 diagrammatically indicates anapplication of system according to the present invention, and,

Figure 2 diagranunatipally' illustrates a modification. Especially inservices for. the distribution of energy by three-phase currents (asindicated in Figure 1)there is often provided, for the low voltagecircuits feeding the lamps, motors and various similar apparatus (2), afourth wire or neutral wire (3) insulated in the same way asotherconductors, but grounded by a connection carefully made between theearth 4 and the neutral point of the secondary windings of each--transformer and disposed in eachsub station supplying a certain number.of sub-.

to protect the low voltage circuit against any accidental contactbetween the primary and 5 negligible. By connecting receiving appa-'ratus (7), rela or the like, which are sensi-- tive only to t isrelatively high frequency current, between the neutral wire and theground (4;) (water main, gas main or the. 0 like) at the subscribersstations, 1t 1s possiscribers. The purpose of this groundingis'afi'ording a low impedance path for currents ble to cause theseapparatus to be operated at will 'by controlling them from thetransformer station, without the addition of speclal wires. A condenser(9) maybe placed in series with the receiver (7 in' order to increasethe syntony and to prevent any flow of current at the periodicity ofthe-distribution. I

A capacity (8), suitably adjusted, may be mounted in parallel with thereactance coil in orderto increase, as already known, the stoppingeflect of this joint-impedance; the condenser can alternatively beconnected across-an additional winding (10) coupled to the coil (5) asshown in Figure 2.

The arrangement described can be applied to all systems of distributioncomprising a neutral wire.

. tion. In this'way, the impedance of the coil is reduced automaticallywhen a short circuit occurs between the high tension lines, the windings1 and the ground.

What I claim is I l. Ina system for signaling over transmission systemshaving an insulated neutral conductor, means for connecting a source ofrelatively high frequency current between said neutral conductor andground, means between said neutral conductor and ground of powerfrequency but a 'high impedance 5 path for currents of signalingfrequency, and signal receiving means responsive to high frequencycurrents connected between the neutral conductor and ground.

2. In a system for signaling over transmission systems having aninsulated neutral conductor, a source of relatively high frequencycurrent between said neutral con ductor and ground, an iron 'cpreinductance coil between said neutral conductor and ground, said coilaffording a low impedance path for currents of power fr uency, butforming a high impedance path orthe currents of signalling frequency,and. signal "re- 00 i I ceiving relays connected between the neutraldimensioned, as to be saturated in case of conductor and ground and inseries with a an increase current circulating between the condenserincreasing the response to high neutralwireand the ground at'the iodi-10 frequency currents and the insulation of neucity of the electricsupply, in orderto reduce 5 tral conductor for power frequency currents.the reactance of'the said periodicity.

3. A system as claimed in claim 1, in 10 which the core of the reactancecoil is so JOSEPH BETHENOD.

